Cipher solver
Cipher Solver: Caesar, Vigenère, Atbash and ROT13 Decoder
Paste a coded message and decode it. Try every Caesar shift at once, run ROT13 or Atbash, turn numbers into letters, or break a Vigenère cipher with a key-length guess.
Cipher
Result
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How they work
The ciphers in this solver
- Caesar and ROT13
- Every letter moves a fixed number of places along the alphabet. ROT13 is the Caesar cipher with a shift of 13, so running it twice returns the original. How to crack a Caesar cipher.
- Atbash
- The alphabet is reversed, so A becomes Z, B becomes Y and so on. There is no key, and applying it twice gives back the text.
- A1Z26
- Each letter is replaced by its position in the alphabet, A as 1 up to Z as 26. Letters in a word are joined with hyphens.
- Vigenère
- A keyword sets a different Caesar shift for each letter, repeating along the message. It hides letter frequencies, but a repeating key leaves a pattern that can be found. How to crack a Vigenère cipher.
- Simple substitution
- Each letter is swapped for a different letter, with no pattern to the swaps. Count the letters, match the most common ones to E, T, A and O, then fill in the rest from the words that start to appear. The letter frequency view and helper above are built for this.
Questions
Common questions
- How do I find out which cipher a message uses?
- Look at the text. If the letters are all shifted by the same amount, Caesar will give readable English in the shift list. If the text contains only numbers from 1 to 26, try A1Z26. If a Caesar shift fails and the letter frequencies look flat, the message may be Vigenère.
- Are spaces, capitals and punctuation kept?
- Yes. Only letters are changed. Capitals stay capitals, and spaces, digits and punctuation pass through as they are.
- Why does the Vigenère key guess need about 100 letters?
- The guess compares how English each column of the text looks once it is split by key length. With fewer letters, each column has too few letters to tell, and the guess is unreliable.
- Can this solve Enigma, Playfair or modern encryption?
- No. This page covers the classic ciphers listed above. Letter frequencies and the substitution helper can handle a simple substitution puzzle, but machine ciphers and modern encryption need other tools.